1. Field of the Invention
The present invention relates to a system which preheats liquid coolant of an engine cooling system, and in particular, it relates to a system which heats the liquid coolant by using the exhaust gas emitted by the engine.
2. Description of the Prior Art
Internal combustion engines operate inefficiently when they are cold. Inefficient engine operation is a severe problem, especially with regard to fuel wastage during the winter in colder climates. In the prior art, many systems and devices have been developed to use the exhaust system of an internal combustion engine to prewarm some engine system, such as the fuel system, or the cooling system, and help bring the engine to an efficient operating temperature more quickly.
Devices and systems to warm the fuel of an internal combustion engine using the exhaust gas are described in the following U.S. Pat. Nos.: Dunner 1,925,032, Holthouse 2,405,145, Smith 3,201,934, Freeman 3,866,919. Heating the fuel aids fuel vaporization which increases engine efficiency, but does not necessarily help in raising the temperature of the engine to an efficient operating temperature more quickly.
Other prior art systems which warm the coolant of the cooling system by using the exhaust gases are described in the following U.S. Pat. Nos.: Mason 1,101,751, Peters 1,260,796, Kelley 2,858,823, Fielder 2,677,359. The Mason and Peters patents show apparatus which would not be desirable in today's motor vehicles. The Kelley patent includes an auxiliary internal combustion engine for heating the coolant of a main engine by using the exhaust gas of the auxiliary engine. The system of the Kelley patent would not be practical on most motor vehicles. The system of the Fielder patent involves using exhaust gas from a combustion type booster heater to heat the coolant, again an impractical idea on most of today's motor vehicles.
Other prior art patents describe systems which use the exhaust gases to heat the coolant of the same internal combustion engine. These U.S. Pat. Nos. are: Furber 1,168,623, Tyson 3,417,920, Wulf 4,095,575. In particular, the above prior art patents show the coolant being automatically diverted by a thermostatically controlled valve to some type of heat exchanger from which heat is transferred from the exhaust gases of the engine. Such systems, however, by diverting substantially all of the coolant into a heat exchanger, disrupt the coolant flow through the radiator and engine.